The present invention relates generally to catheters having an expandable balloon and to premounted balloon expandable stent balloon catheters, and specifically to a balloon catheter with expansion means at the distal end of the balloon. The present invention is particularly directed to improved arrangements of the balloon member of a balloon catheter which provides inflation of the balloon from its distal end to its proximal end, and to improved arrangements of a stent delivery catheter which provides expansion of the stent from its distal end to its proximal end.
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure which is well established for the treatment of blockages in the coronary arteries. Blockages may occur from cholesterol precipitation on the coronary wall which may be in any stage from initial deposit through aged lesions. Coronary arteries may also become blocked due to formation of thrombus. Percutaneous transluminal angioplasty (PTA) is also a known treatment of body lumens.
The most widely used form of percutaneous angioplasty makes use of a dilatation balloon catheter. In typical PTCA or PTA procedures, the cardiovascular system of a patient is accessed with an introducer, usually via the femoral artery or the radial artery. All other devices including a guiding catheter are percutaneously introduced into the cardiovascular system of a patient through the introducer and advanced through a vessel until the distal end thereof is at a desired location in the vasculature. A guide wire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guide wire sliding through the dilatation catheter. The guide wire is first advanced out of the guiding catheter into the patient's coronary vasculature and the dilatation catheter is advanced over the previously advanced guide wire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the flexible, expandable, preformed balloon is inflated to a predetermined size with a fluid at relatively high pressures, such as greater than about four atmospheres, to radially compress or fracture the atherosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patients vasculature and blood flow resumed through the dilated artery.
Following angioplasty procedures of the kind described above, there is a possibility of restenosis of the artery. Restenosis may necessitate either another angioplasty procedure, a surgical by-pass operation, or some method of repairing or strengthening the area. To reduce the likelihood of restenosis and strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, called a stent, inside the artery at the lesion. In general, stents are prosthetic devices which can be positioned within a body cavity, for example, a blood vessel of the body of a living human or in some other difficulty accessible place. A stent generally has a variable diameter, which may be increased or decreased. Stents are particularly useful for permanently widening a vessel which is in a narrowed state, or for internally supporting a vessel damaged by an aneurysm.
Such stents are typically introduced into the body cavity by use of a catheter. The catheter is usually of the balloon catheter type in which the balloon is utilized to expand the stent, which is positioned over the balloon, to place it in a selected location in the body cavity. The stent is expanded to a larger diameter for placement in the vasculature, often by the balloon portion of the catheter. Stents delivered to a restricted coronary artery, expanded to a larger diameter by a balloon catheter, and left in place in the artery at the site of a dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer and U.S. Pat. No. 5,007,926 to Derbyshire.
One important characteristic of a dilatation balloon catheter is the manner in which the balloon inflates. Prior art balloon catheters are constructed such that the inflation fluid enters the balloon at the proximal end. The balloon catheter of the present invention provides a construction wherein the fluid enters the balloon at the distal end thereof, resulting in expansion of the balloon from its distal end to its proximal end. When used with balloon expandable stents, the balloon and balloon catheter of the present invention allows for the stents to dilate distally first and then expand proximally. Current designs have stents either "dumbbell", i.e. open at both ends, or open proximally first. The distal inflation provided by the present invention prevents the release or dislodgment of thrombus or plaque downstream. In addition, distal to proximal inflation serves to minimize vessel wall trauma resulting from stent "dumbbelling".